The invention relates to a housing part of plastic.
To increase convenience for the user, locking systems for motor vehicles are often equipped with an electronic key. After appropriate actuation by the user, a code is exchanged, for example by means of electromagnetic waves, between the key and the locking system, so that after positive evaluation of the code the doors and the trunk lid of the motor vehicle are unlocked or locked by remote control and other functions are initiated.
An electronic key of this type, which is known from DE 196 05 201 A1, has a housing of plastic. Arranged on a housing part are actuating members for electrical switches for the manual initiation of functions of the locking system. The electrical switch is arranged on a printed-circuit board located in the housing, the actuating member acting in an actuating manner on a plunger of the electrical switch via an opening in the housing part. The actuating member is designed in the manner of a surface which extends essentially in the surface of the housing part and can be elastically deformed for the actuation.
For sealing the housing against the ingress of contaminants in the region of the actuating members, an elastic sealing element which covers the opening in the sealing part is arranged between the actuating member and the electrical switch. The sealing element may be welded or else molded onto the edge of the opening in the housing part. The production of the additional sealing element is complicated and laborious.
The invention is based on the object of achieving a reliable sealing of the housing part in the region of the actuating member by simple means. In particular, the production of the housing part is to be simplified.
The invention is based on the basic idea of providing a supporting element for the actuating member, the supporting element and the actuating member being prefabricated as half-parts. In the production of the housing part taking place by injection molding, the two half-parts are encapsulated along at least a part of their edge with the plastic for the housing part. As a result, the actuating member together with the supporting element is embedded in the housing part in such a way that the actuating member itself serves for the sealing of the opening in the housing part and is nevertheless movable for the actuation of the electrical switch.
For simple handling in the production of the housing part, it is appropriate to provide for the actuating member on the supporting element a fastening of such a type that the two half-parts form a joint component for the encapsulation with the plastic of the housing part. The fastening may be produced by a force closure and/or a form fit.
For example, pegs, catch hooks, snap hooks or the like on one half-part may engage in corresponding receptacles on the other half-part. Furthermore, one of the half-parts, in particular the supporting element, may have through-holes. The through-holes are filled with plastic of the housing part during the encapsulation. This achieves a particularly good anchorage of the supporting element together with the actuating member in the housing part.
For the actuating action on the plunger of the electrical switch, the actuating member is assigned an attachment which is movable in the direction of the electrical switch. This attachment may be arranged in the manner of a peg approximately in the center of the actuating member on the side facing the supporting element. In the supporting element there is an opening which corresponds to the attachment and into which the attachment protrudes to act on the plunger.
In an embodiment which may be appropriate when using a soft-elastic material for the actuating member, the attachment is formed in one piece with the actuating member. For this purpose, the attachment is molded onto the actuating member in the production of the half-part. In another embodiment, which may be appropriate in particular when using a hard-elastic material for the actuating member, the attachment comprises a part which is separate from the actuating member, the actuating member bearing against the attachment with a part of its side facing the electrical switch. The attachment is expediently arranged by means of a spring-like element at the opening in the supporting element. The spring-like element may be designed in the manner of a torsion spring of plastic, the spring-like element being molded in one piece onto the opening in the supporting element on the one hand and onto the attachment on the other hand.
If the supporting element is designed for simultaneously receiving a plurality of actuating members, the production of a housing part with a plurality of actuating members can be simplified. The actuating members are fastened as individual half-parts on this supporting element to form a component. Equally well, a plurality of actuating members may also be formed as a one-piece half-part, which is then fastened on the supporting element, with a component in turn being formed. For the encapsulation with the plastic of the housing part, only this one component then has to be handled. The actuating member may be designed as an elongate part with rounded-off corners and/or rounded-off sides, as an oval part, as a round part or as a circular part or may have some other desired shape. The supporting element has in turn a shape corresponding approximately to the actuating member or to the actuating members.
In a development, the supporting element is designed in the manner of an essentially planar plate and the actuating member is designed in the manner of an elastically deformable membrane, if appropriate having a curvature. The elasticity of the membrane is then fixed by its thickness in dependence on the hardness of the plastic. Suitable as the plastic for the actuating member is on the one hand a soft, elastic plastic, such as a thermoplastic elastomer. In particular, the thermoplastic elastomer may be a block copolymer of polybutylene terephthalate and polyether glycol. On the other hand, a hard plastic, such as polyamide, polyacetal or the like, is also suitable for the actuating member. The housing part consists of a hard plastic, for example of polyamide, which may be glass-fiber filled or glass-bead filled.
The supporting element expediently likewise consists of a hard plastic. It may be appropriate to use a plastic which is largely transparent to light in at least a partial range of the visible spectrum, such as polycarbonate, transparent amorphous polyamide or the like. In this case, a lighting element can be integrated in the housing part in a particularly simple way. For this purpose, a portion of an approximately lenticular or cylindrical form may be arranged on the supporting element in one piece via a carrier part. This portion is then encapsulated with the plastic of the housing part in such a way that the portion forms a window molded into the wall of the housing part.
In the invention, the actuating member itself serves as the sealing means, so that it is possible to dispense with an additional sealing element. Nevertheless, reliable sealing of the housing is achieved in the region of the actuating members, whereby a functionally reliable electronic key is obtained.
Since there is no need for an additional sealing element, which is difficult to produce or process, the production of the housing part according to the invention is simplified. As a result, cost savings are in turn achieved. In particular, the supporting element has the effect of dimensionally stabilizing the actuating member, which in itself as an individual part is flaccid, and, as a result, is easier to handle when placing into the injection mold during the production of the housing part.
Further advantages achieved by the invention are, in particular, that there is great freedom in the choice of materials for the housing part and the actuating member. In the case of the previously known housing part, only certain material combinations are possible on account of the necessary production conditions and they do not allow, for example, a free choice of colors for the actuating members. The actuating members of the housing part according to the invention can advantageously be colored as desired. Furthermore, printing the desired symbols onto the actuating members or laser inscription of the actuating members is possible. The use of partially transparent materials for the actuating members allows them to be designed such that they can be illuminated with functional and/or search lighting. It is plainly evident that a multitude of design possibilities for the electronic key have now been opened up.